/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.messaging.handler;

import java.util.Collection;
import java.util.Iterator;

import org.springframework.lang.Nullable;

/**
 * Base class for {@code MessageCondition's} that pre-declares abstract methods
 * {@link #getContent()} and {@link #getToStringInfix()} in order to provide
 * implementations of {@link #equals(Object)}, {@link #hashCode()}, and
 * {@link #toString()}.
 *
 * @author Rossen Stoyanchev
 * @since 4.0
 */
public abstract class AbstractMessageCondition<T extends AbstractMessageCondition<T>>
        implements MessageCondition<T> {


    /**
     * Return the collection of objects the message condition is composed of
     * (e.g. destination patterns), never {@code null}.
     */
    protected abstract Collection<?> getContent();

    /**
     * The notation to use when printing discrete items of content.
     * For example " || " for URL patterns or " && " for param expressions.
     */
    protected abstract String getToStringInfix();


    @Override
    public boolean equals(@Nullable Object obj) {
        if (this == obj) {
            return true;
        }
        if (obj != null && getClass() == obj.getClass()) {
            AbstractMessageCondition<?> other = (AbstractMessageCondition<?>) obj;
            return getContent().equals(other.getContent());
        }
        return false;
    }

    @Override
    public int hashCode() {
        return getContent().hashCode();
    }

    @Override
    public String toString() {
        StringBuilder builder = new StringBuilder("[");
        for (Iterator<?> iterator = getContent().iterator(); iterator.hasNext(); ) {
            Object expression = iterator.next();
            builder.append(expression.toString());
            if (iterator.hasNext()) {
                builder.append(getToStringInfix());
            }
        }
        builder.append("]");
        return builder.toString();
    }

}
